1. Field of the Invention
The present invention relates to an electron emission device, and in particular, to an electron emission device and a method of manufacture thereof in which the electron emission device has various functional electrodes in addition to the electrodes serving to emit electrons.
2. Description of Related Art
Generally, electron emission devices are classified into a first type where a hot cathode is used as an electron emission source, and a second type where a cold cathode is used as the electron emission source. Among the second type of electron emission devices are a Field Emitter Array (FEA) device, a Metal-insulator-metal (MIM) device, a Metal-insulator-semiconductor (MIS) device, a Surface Conduction Emitter (SCE) device, and a Ballistic electron Surface Emitter (BSE) device.
In the FEA electron emission device, electron emission regions are formed by a material emitting electrons under the application of an electric field, and driving electrodes, such as cathode and gate electrodes, arranged around the electron emission regions. When an electric field is formed around the electron emission regions due to the voltage difference between the two electrodes, electrons are emitted from the electron emission regions.
The cathode and the gate electrodes cross each other while interposing an insulating layer, thereby forming a matrix structure. When the crossed region of the two electrodes is defined as a pixel region, the electron emission at the respective pixels is controlled by the scan signal applied to any one of the electrodes and the data signal applied to the other electrode. A square wave is applied to the cathode and the gate electrodes, the square wave having both Direct Current (DC) characteristics as well as Alternating Current (AC) characteristics. The square wave is a relatively high voltage, and has a short “ON” time that varies somewhat depending upon the number of pixels.
Accordingly, with the usual electron emission device, the driving waveform can be easily distorted due to the internal factors of the device, such as the internal resistance of the cathode and gate electrodes, and the electric potentials accumulated between the two electrodes. More particularly, among the electrodes receiving the scan signals, signal distortion can easily occur with the row of electrodes first receiving the scan signal and with the row of electrodes last receiving the scan signal.
When the signal distortion occurs during the driving of the electron emission device, unnecessary electron emission occurs at the signal-distorted pixels, or the necessary electron emission does not occur at the relevant pixels. As a result, the correct on/off control of the pixels becomes impossible, and a precise image display does not occur.
With most electron emission devices, the inner space thereof is exhausted to be in a vacuum state, and a remnant gas therein is collected and removed using a getter, thereby heightening the degree of vacuum.
The getters are classified into evaporable getters, and non-evaporable getters. The evaporable getter is well adapted for a vacuum display device with a sufficient inner space, such as a cathode ray tube, and has excellent remnant gas collection efficiency. However, most of the electron emission devices have a very narrow inner space as the distance between the front and the rear substrates thereof is 2 mm or less. Therefore, it is difficult to arranged a getter with a predetermined volume in a narrow inner space, and to apply the evaporable getter due to the narrow space between the electrodes arranged on the substrate. With the electron emission device, a non-evaporable getter is installed external to the display region, and activated to remove the remnant gas after the exhausting.
However, compared to the evaporable getter, the non-evaporable getter has a low remnant gas collection efficiency, and hence, it is difficult to increase the degree of vacuum. This makes the device structure and the processing steps complicated. Particularly with the FEA typed electron emission device using a carbonaceous material for the electron emission regions, the carbonaceous material easily reacts with a particular remnant gas, such as oxygen, and reduces the life span and the electron emission efficiency of the electron emission regions. Consequently, with the electron emission device using a carbonaceous material, the remnant oxygen-containing gas should be removed after the exhausting, and this is effected with gettering.